Flexible member

ABSTRACT

An improved flexible member of the type designed for use in a fluid pressure system having the predetermined flex wrinkle pattern or a modification thereof imparted to its surface to improve the flexing properties while the member is operating in such system. This pattern may consist of a simulation of the actual flex wrinkle pattern of a previously operating flexible member or be a compromise which employs a plurality of grooves having substantially the same pitch as the wrinkles. Also, the method by which the pattern is imparted to the surface of the flexible member. This invention results in the increased flex life and improved low temperature performance of the flexible member.

United States Patent 2,830,622 4/1958 Robertsetal {72] Inventor Thomas E. Barkley Akron, Ohio 211 Appl. No. 679,731 [22] Filed Nov. 1, 1967 [45] Patented Aug. 10, 1971 [7 3] Assignee The Goodyear Tire & Rubber Company Summit, Ohio [541 FLEXIBLE MEMBER 12 Claims, 8 Drawing Figs.

[52] U.S.CI.. 138/119, 92/34 [51] 1nt.Cl .v F161 11/00 [50] Field ofSearch 138/120, 4 121,122,129, 119; 92/34; 285/226 [561 References Cited UNITED STATES PATENTS 2,341,556 2/1944 .Ioy 92/34 X 2,606,442 8/1952 Raines 92/34 X 138/121 3,071,161 1/1963 Ulrich 138/120 3,388,705 6/1968 Grosshandler 285/226 X 3,411,157 11/1968 Rabenhorst 285/226 X FOREIGN PATENTS 1,258,058 5/1960 France 285/226 Primary ExaminerFred C. Mattem, Jr. Assistant Examiner-Henry K. Artis Attorneys-F. W. Brunner and Robert 11. Hatton ABSTRACT: An improved flexible member of the type designed for use in a fluid pressure system having the predetennined flex wrinkle pattern or a modification thereof imparted to its surface to improve the flexing properties while the member is operating in such system. This pattern may consist of a simulation of the actual flex wrinkle pattern of a previously operating flexible member or be a compromise which employs a plurality of grooves having substantially the same pitch as the wrinkles. Also, the method by which the pattern is imparted to the surface of the flexible member. This invention results in the increased flex life and improved low temperature performance of the flexible member. 1

PATENIEUAUBIOIQH 3,598,155

SHEEI 1 [1F 2 FIG. 2

FIG. 3

FIG. 4

I NVENTOR.

ATTOR N EY THOMAS E. BURKLEY PATENTEnAuBmmn 77,598,155

SHEET 0F 2 INVENTOR THOMAS E. BURKLEY '5 8 20 zwxzw-n ATTOR NEY FLEXIBLE MEMBER This invention relates to an improved flexible member of the type designed for use in a fluid pressure system and the method of producing such flexible member. More specifically, this invention relates to a flexible member of the type used, for example, in a pneumatic suspension or brake control system referred to generally as the rolling lobe air spring and rolling sleeve diaphragm respectively.

Rolling lobe air springs are normally employed for shock absorbing, load supporting and vibration isolation in vehicle suspension systems and other industrial and military applications. The typical pneumatic pressure system of this type operates as follows: A tubular essentially cylindrical flexible member of fabric reinforced elastomeric material such as rubber or the like is positioned between retaining elements. This flexible member has clamping means at the peripheral edge portions thereof in order to attach the member to the retaining elements and form an airtight chamber capable of supporting a load of varying proportions. A piston, acting upon the flexible member, creates a rolling motion in the sidewall of the flexible member consequently causing the compression and expansion of the column of air confined in the chamber. An excellent detailed description of the construction, operation, and production of the rolling lobe-type air spring is contained in Hirtreiter US. Pat. No. 3,043,582.

Similarly, rolling or sleeve diaphragms of the type used in pneumatic brake control systems employ a cup or hat-shaped flexible fabric reinforced member of elastomeric material with a cylindrical or frustoconical sidewall which may have a closed base or may be open on both ends. The peripheral edge portion or lip of the diaphragm typically is attached to the central wall portion of a brake chamber. The closed end portion or the other peripheral edge portion of the open end attached to the piston thus forms an airtight compartment. In some instances, when air under pressure is admitted into this compartment, the diaphragm is deflected thereby creating a rolling motion in the sidewall of the diaphragm to move a plunger contained within the brake chamber.

Those skilled in the art are aware that one of the major problems encountered in such systems is the premature failure of the flexible member due to flex cracking in the area which is subjected to the maximum flexing during operation in such systems. This cracking may also occur prematurely when the flexible member is exposed to extremely low temperatures in frigid areas as the result of the consequently stiffened condition of the elastomeric material after such exposure.

The present invention discloses flexible diaphragms or members of an improved construction which prolongs substantially the flex life even under severe low temperature conditions as well as a method of producing such a flexible member. It has been found that forming, prior to installation I i in a fluid system, the flex wrinkle pattern on the surface of the flexible member at least in the area subjected to the maximum flexing, will control the flex characteristics and alleviate many of the normal deteriorating stresses when the flexible member is operating in the system. In other words, the actual flex wrinkle pattern is effectively simulated on the compression surface of the flexible member with the wrinkles therein acting as hinge points which facilitate the flexing in the area of the member most susceptible to failure or cracks due to flexing or low temperatures.

This is accomplished by reproducing on the compression surface of the flexible member, the actual flex wrinkle pattern created on the compression surface of a flexible member by the operation of a similar diaphragm in a fluid pressure system for a period of time sufficient to create the flex wrinkle. This may be accomplished in a number of ways, some of which will be hereinafter described.

The primary object of this invention is to provide a method which will control the flex characteristics and alleviate the stresses created in a flexible member to provide a substantial improvement in the general durability thereof without an ap preciable increase in manufacturing costs.

Another important object of this invention is to significantly prolong the flex life of a flexible elastomeric member of the type used in a fluid pressure system such as an air spring suspension or pneumatic brake control system.

Still another object of this invention is to provide an improved flexible elastomeric member such as a rolling lobe air spring and rolling sleeve airbrake diaphragm which will resist wall cracking when the product is operating during extreme cold weather exposures.

A further object of this invention is to facilitate the operation ofa flexible member of the type designed for use in a fluid pressure system by providing an improved contour to reduce resistance to the rolling motion of such member particularly at low pressures.

Other objects and advantages of this invention will become apparent hereinafter as the description thereof proceeds, the novel features, arrangements and combinations being clearly pointed out in the specification as well as the claims thereunto appended.

FIG. I is a perspective view of one type of flexible member illustrating this invention;

FIG. 2 is a section taken substantially through 2-2 of FIG. I;

FIG. 3 is a modification of the invention shown in FIG. 2;

FIG. 4 is an elevation showing one method of producing the invention shown in FIG. 3;

FIG. 5 is a modification of the invention shown in FIG. 3;

FIG. 6 is another modification of the invention shown in FIG. 3;

FIG. 7 is a perspective view of another type of flexible member for which this invention is useful; and

FIG. 8 is a section taken substantially through 8-8 of FIG. 7 to more clearly illustrate the invention.

Although specific examples will be illustratedshowing certain common types of applications of flexible members, it is to be understood that the concept disclosed in this invention is equally applicable to flexible members of all sizes and shapes. These particular features will depend upon the apparatus in which the members are used. It should also be noted that although particular reference is made to pneumatic systems, the principle disclosed in this invention will apply equally to other fluid systems which use various liquids or gases such as oil or nitrogen.

For the purposes of illustration, FIG. 1 shows a flexible member 1 which, in this example, is of the type used in vehicle shock absorber systems referred to as a sleeve-type rolling lobe air spring. As illustrated, this flexible member 1 is tubular with an essentially elongated cylindrical shape having an inside diameter of approximately 1-1 1/16 inches and a wall thickness of 0.110, plus or minus 0.010 inch and is generally about 1 foot in length. Preferably, it is formed of rubber or other elastomeric material with a fabric reinforcement contained therein.

FIG. 2, a sectiontaken through 2-2 of FIG. 1, illustrates the cord fabric reinforcement 2, usually nylon, and the normal flex wrinkle pattern 3 reproduced on the inner surface 4 of flexible member I. The pattern 3 has been reproduced from the actual flex wrinkle pattern of a flexible member which has been subjected to normal operating conditions in a vehicle suspension system or facsimile thereof (such as a flex test unit) for a sufficient period of time to create the wrinkle pattern. Due to the particular operating characteristics of the rolling lobe air spring, the actual flex wrinkle pattern is formed on the inner or compression surface of the rolling torus of the flexible member. In this way, the actual flex wrinkle pattern is simulated on the inner surface 4 of the flexible member I with the wrinkles 5 acting as hinge points to locate and alleviate the stresses that will be created when flexible member I is operating in the system. The depth of the wrinkles Sin the actual or simulated wrinkle pattern is generally in'the range of 0.005 to 0.018 inch but, of course, will vary-depending upon the length of time that the flexible member has been operating. Obviously, it is essential to reproduce the pattern 3 in at least the area of the flexible member I which is subjected to the maximum flexing. The location and extent of the area will depend upon the particular application and consequently must be determined for each application.

Various methods may be used to reproduce the actual flex wrinkle pattern thereby forming the predetermined flex wrinkle pattern on the surface of the flexible member. One method successfully employed is as follows:

I. Make a longitudinal cut in the flexible member of the rolling lobe air spring after it has operated for a sufflcient period to create a flex wrinkle pattern.

2. Cut out the portion of the flexible member which has been subjected to the maximum flexing and therefore contains the actual flex wrinkle pattern.

. Mount this portion on a substantially flat base by means of an adhesive.

4. Enclose the periphery of the mounted portion to form a mold.

5. Form a pattern of an opposite configuration or contour from that of the actual flex wrinkle pattern by pouring a substance such as polyurethane into this mold.

6. Attach the polyurethane pattern to a mandrel or molding core so as to be substantially flush with the surface. Preferably, the pattern is adhered to the mandrel by means of an adhesive vulcanized under heat and pressure.

7. Place a sleeve of unvuleanized elastomeric material over the mandrel then vulcanize under heat and pressure to produce the simulated flex wrinkle pattern on the inner surface of the flexible member.

The foregoing method, although effective, has the disadvantage of being time-consuming and too costly when a large number of patterned mandrels must be produced to meet the production requirements of the flexible sleeves. Therefore, a compromise procedure has been developed in which the flex wrinkle pattern is approximated by determining the common or predominate distance or pitch of adjacent wrinkles of the actual flex wrinkle pattern then producing a plurality of grooves or corrugations at this spacing on the inner surface of the flexible member. The grooves are formed preferably in the surface of the flexible member during molding under heat and pressure but other methods may also be used, such as machining the grooves on the already vulcanized product. As a minimum, these grooves are placed in the portion of the flexible member which will be subjected to the maximum flexing during its operation in the fluid pressure system, but for convenienee, they may be formed in other areas as well without affecting the operation of the flexible member.

Although any type of corrugated or convoluted contour will act to relieve the stresses in the flexible member, it is important that alternate flat or land portions of greater width than the grooves be provided between the grooves. This will prevent objectionable noise transfer and the possible inter leaving of the corrugations during the rolling motion of the flexible member.

In the just described procedure, the grooves act as the hinge points to locate and alleviate the stresses created during the operating of the flexible member thus serving in much the same manner as the wrinkles of the flex wrinkle pattern. In addition, since the grooves are uniformly spaced, this structure has the advantage of uniformly located stress areas to provide for a uniform distribution of the stresses when the flex member is operating. It has been determined that the best general durability is obtained with a groove depth of 0.0l to 0.018 inch. In cold weather, in addition to the advantage of the hinge points provided by the corrugations, the reduced wall gauge at the grooves also imparts more flexibility to the flexible members. Furthermore, the grooves act to facilitate the operation of the flexible member by reducing the re sistance to the rolling motion particularly at low pressures. These grooves may take various forms as will become apparent.

One form ofthe invention shown in FIG. 3 illustrates a flexible member produced by using the compromise procedure. The flexible member I is again of the type used in a rolling lobe air spring and has circumferential grooves 6 and alternate flat or land portions 7 uniformly positioned longitudinally along substantially the entire length of the flexible member 1. The pitch 8 of the grooves 6 is substantially equal to pitch 9 of the wrinkles 5 shown in FIG. 2. In theory, the wrinkle pitch 9 is generally determined by such characteristics as the size, shape, wall thickness, inflation diameter, and roll radius of the flexible member as well as by the design of the particular piston assembly. For example, it has been determined that a flexible sleeve ofa rolling lobe air spring with an inside diameter of l-l Ill 6 inches after operating for a period of one million cycles in a flex test unit has a wrinkle pitch of approxi mately one-eighth inch. Also it has been determined that this type flexible sleeve when removed from a vehicle shock-absorbing system after 25,000 miles of normal usage developed essentially this same pitch. Accordingly, the pitch 8 of the grooves 6 should also be one-eighth inch. As previously mentioned, grooves 6 take the place of the wrinkles 5 of the predetermined flex wrinkle pattern 3 to control the flexing and alleviate the stresses in the flexible member I. As shown, a series of longitudinal ribs 10 are formed on the surface of the flexible member, from a series of corresponding longitudinal grooves in the mold, the purpose of which will be explained later.

One method of forming these circumferential grooves is shown in FIG. 4. As illustrated, a steel mandrel or molding core 11 has a plurality of circumferential ridges or peaks 12 on the outer surface and uniformly spaced along the length thereof with alternating flat or land portions 13 of greater width than the ridges l2 therebetween. Preferably, longitudinally extending grooves 14 on the surface of mandrel ll serve as venting means to permit, during the molding operation, the escape of trapped air. The flexible member 1 is positioned over the mandrel 11 and vulcanized under heat and pressure thus forming grooves 6 and flat portions 7, as well as ribs 10 on the inner surface 4 of the flexible member 1.

FIG. 5 is a modification of the invention shown in FIG. 3 in which the flexible member 1 contains a plurality of helical grooves 6A molded on its inner surface 4.

Another modification of the invention shown in FIG. 3 is illustrated in FIG. 6 in which flexible member IA is tapered gradually in the longitudinal direction. The purpose of the tapered design is to further facilitate the functioning of the flexible sleeve rolling lobe air spring member which tends to take on a longitudinally tapered configuration after extended periods of operation. Of course, the grooves 6 may also be either circumferential or helical in this design. It is also important to recognize that in addition to the rolling lobe-type air spring, the teaching of this invention may be applied to all piston-type air springs with little or no modification required.

Another type of flexible member of the same general classification as that used in the rolling lobe air spring is the rolling sleeve diaphragm shown in FIG. 7 which is used in airbrake control systems. Flexible member lB normally ofa cup or hatshaped configuration with closed base 15 and a cylindrical sidewall 16. It is generally composed of elastomeric material such as rubber or the like and reinforced by a textile cord or square woven fabric such as cotton or nylon. However, it may also contain no reinforcement and be formed of a material such as polyurethane. The maximum flexing in this member takes place on the inner or compression surface 17 of the rolling torus which is in proximity to the peripheral edge portion or lip I8 at the open end I9 of the flexible member 18. The predetermined flex wrinkle pattern may be imparted to this area of the flexible member 18 by means ofa mold (not shown) having a molding surface of opposite configuration from that of the actual flex wrinkle pattern. Here again, however, it is much more practical and economicalto use a molding surface, as previously described, containing a plurality of ridges or peaks positioned in the area of maximum flexing and having the required pitch between the ridges to form the product as shown in FIG. 8.

FIG. 8 is a section taken through 8-8 of FIG. 7 showing the fabric reinforcement 20 and a plurality of essentially circular grooves 21 substantially adjacent to the peripheral edge portion 18 on the inner surface 17- at the open end 19 of flexible member 18. These grooves 21, of course, function in the manner mentioned previously. Although particular reference has been made to the rolling sleeve diaphragm, it should be apparent to those skilled in the art that the invention is equally applicable to other forms of flexible diaphragms such as the long stroke, convoluted, or dished type.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

lclaim:

l. A flexible tubular member having at least one end open and of the type designed for use in a fluid pressure system in which said member undergoes movement causing a rolling motion therein which creates a flex wrinkle pattern on a surface of the member after a period of flexing during the operation of such system, said member having a plurality of grooves in at least the area thereof subjected to the maximum flexing during the movement of said member, said grooves positioned to substantially simulate and correspond to the actual flex wrinkle pattern created on a surface ofa similar flexible tubular member which has been previously operated in a fluid pressure system, thereby forming a plurality of hinge points to control flexing of said member and distribute the resulting stresses in said member caused by the rolling motion thereof.

2. A flexible member as claimed in claim 1 wherein the distance between the centerline of each adjacent groove is substantially equal to the distance between the centerline of each adjacent wrinkle of the actual flex wrinkle pattern with the grooves being uniformly spaced on the surface of said member.

3. A flexible member as claimed in claim 2 of the type used in vehicle shock absorber and suspension systems, comprising a tubular sleeve of fabric reinforced elastomeric material containing a plurality of circumferential grooves uniformly positioned on the inner surface thereof and lands of greater width than said grooves alternately disposed therebetween thereby preventing objectionable noise transfer.

4. A flexible member as claimed in claim 2, of the type used in airbrake diaphragm fluid pressure systems, comprising an essentially hat-shaped member of fabric reinforced elastomeric material containing a plurality ofcircular grooves uniformly positioned on the inner surface and adjacent the peripheral edge of the open end thereof.

5. A flexible member as claimed in claim 3 in which the grooves are positioned helically on the inner surface thereof.

6. A flexible member as claimed in claim 3 having a tapered configuration at one end thereof.

7. In a fluid pressure system including the combination of a body structure and a flexible tubular member having at least one end open which is attached to the body structure to create a fluidtight chamber, said body structure containing elements movable relative to each other with the movement causing a rolling motion in the flexible member which creates a flex wrinkle pattern on the surface of the member after a period of flexing during the operation of such system, the improvement wherein said member includes a plurality of grooves in at least the area of the surface thereof subjected to the maximum flexing during the movement of the member, said grooves positioned to substantially simulate and correspond to the actual flex wrinkle pattern created on a surface of a similar flexible tubular member which has been previously operated in a fluid pressure system, thereby forming a plurality of hinge points to control flexing 0f the member and distribute the resulting stresses in said member caused by the rolling motion thereof.

8. A flexible member as claimed in claim 7 wherein the distance between the centerline of each adjacent groove is substantially equal to the distance between the centerline of each adjacent wrinkle of the actual flex wrinkle pattern with the grooves being uniformly spaced on the surface of said member.

9. A flexible member as claimed in claim 8 of the type used in vehicle shock absorber and suspension systems, comprising a tubular sleeve of fabric-reinforced elastomeric material containing a plurality of circumferential grooves uniformly positioned on the inner surface thereof and lands of greater width than said grooves alternately disposed therebetween thereby preventing objectionable noise transfer.

l0. A flexible member as claimed in claim 8 ofthe type used in airbrake diaphragm fluid pressure systems, comprising an essentially hat-shaped member of fabric-reinforced elastomeric material containing a plurality of circular grooves uniformly positioned on the inner surface and adjacent the peripheral edge of the open end thereof.

I]. A flexible member as claimed in claim 9 in which the grooves are positioned helically on the inner surface thereof.

12. A flexible member as claimed in claim 9 having a tapered configuration at one end thereof.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,598 ,155 Dated August 10, 1971 Inventoflg) Thomas E. Burkley It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the cover sheet [73] "Summit, Ohio" should read Akron, Ohio Column 4, line 54, after "1B" insert Signed and sealed this 27th day of June 1972.

(SEAL) Attest:

EDWARD M. FLETCHER,JR.

ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-105O (10-69) USCOMM-DC 603764- 69 n u 5 GOVERNMENT PRINYING urncz: I969 o-asa-sn 

1. A flexible tubular member having at least one end open and of the type designed for use in a fluid pressure system in which said member undergoes movement causing a rolling motion therein which creates a flex wrinkle pattern on a surface of the member after a period of flexing during the operation of such system, said member having a plurality of grooves in at least the area thereof subjected to the maximum flexing during the movement of said member, said grooves positioned to substantially simulate and correspond to the actual flex wrinkle pattern created on a surface of a similar flexible tubular member which has been previously operated in a fluid pressure system, thereby forming a plurality of hinge points to control flexing of said member and distribute the resulting stresses in said member caused by the rolling motion thereof.
 2. A flexible member as claimed in claim 1 whereiN the distance between the centerline of each adjacent groove is substantially equal to the distance between the centerline of each adjacent wrinkle of the actual flex wrinkle pattern with the grooves being uniformly spaced on the surface of said member.
 3. A flexible member as claimed in claim 2 of the type used in vehicle shock absorber and suspension systems, comprising a tubular sleeve of fabric reinforced elastomeric material containing a plurality of circumferential grooves uniformly positioned on the inner surface thereof and lands of greater width than said grooves alternately disposed therebetween thereby preventing objectionable noise transfer.
 4. A flexible member as claimed in claim 2, of the type used in airbrake diaphragm fluid pressure systems, comprising an essentially hat-shaped member of fabric reinforced elastomeric material containing a plurality of circular grooves uniformly positioned on the inner surface and adjacent the peripheral edge of the open end thereof.
 5. A flexible member as claimed in claim 3 in which the grooves are positioned helically on the inner surface thereof.
 6. A flexible member as claimed in claim 3 having a tapered configuration at one end thereof.
 7. In a fluid pressure system including the combination of a body structure and a flexible tubular member having at least one end open which is attached to the body structure to create a fluidtight chamber, said body structure containing elements movable relative to each other with the movement causing a rolling motion in the flexible member which creates a flex wrinkle pattern on the surface of the member after a period of flexing during the operation of such system, the improvement wherein said member includes a plurality of grooves in at least the area of the surface thereof subjected to the maximum flexing during the movement of the member, said grooves positioned to substantially simulate and correspond to the actual flex wrinkle pattern created on a surface of a similar flexible tubular member which has been previously operated in a fluid pressure system, thereby forming a plurality of hinge points to control flexing of the member and distribute the resulting stresses in said member caused by the rolling motion thereof.
 8. A flexible member as claimed in claim 7 wherein the distance between the centerline of each adjacent groove is substantially equal to the distance between the centerline of each adjacent wrinkle of the actual flex wrinkle pattern with the grooves being uniformly spaced on the surface of said member.
 9. A flexible member as claimed in claim 8 of the type used in vehicle shock absorber and suspension systems, comprising a tubular sleeve of fabric-reinforced elastomeric material containing a plurality of circumferential grooves uniformly positioned on the inner surface thereof and lands of greater width than said grooves alternately disposed therebetween thereby preventing objectionable noise transfer.
 10. A flexible member as claimed in claim 8 of the type used in airbrake diaphragm fluid pressure systems, comprising an essentially hat-shaped member of fabric-reinforced elastomeric material containing a plurality of circular grooves uniformly positioned on the inner surface and adjacent the peripheral edge of the open end thereof.
 11. A flexible member as claimed in claim 9 in which the grooves are positioned helically on the inner surface thereof.
 12. A flexible member as claimed in claim 9 having a tapered configuration at one end thereof. 